Really fix avcodec avec block_Realloc change.

modules/codec/avcodec/video.c

@@ -533,6 +533,7 @@ picture_t *DecodeVideo( decoder_t *p_dec, block_t **pp_block )
                             p_block->i_buffer + FF_INPUT_BUFFER_PADDING_SIZE );
         if( !p_block )
             return NULL;
+        p_block->i_buffer -= FF_INPUT_BUFFER_PADDING_SIZE;
         *pp_block = p_block;
         memset( p_block->p_buffer + p_block->i_buffer, 0,
                 FF_INPUT_BUFFER_PADDING_SIZE );